<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width">
<style>
html, body {
    margin: 0;
    padding: 0;
    height: 100%;
    overflow: hidden;
}
#video {
    width: 100%;
    height: 100%;
    background: black;
}
</style>
</head>
<body>

<script>

const restartPause = 2000;

const unquoteCredential = (v) => (
    JSON.parse(`"${v}"`)
);

const linkToIceServers = (links) => (
    (links !== null) ? links.split(', ').map((link) => {
        const m = link.match(/^<(.+?)>; rel="ice-server"(; username="(.*?)"; credential="(.*?)"; credential-type="password")?/i);
        const ret = {
            urls: [m[1]],
        };

        if (m[3] !== undefined) {
            ret.username = unquoteCredential(m[3]);
            ret.credential = unquoteCredential(m[4]);
            ret.credentialType = "password";
        }

        return ret;
    }) : []
);

const parseOffer = (offer) => {
    const ret = {
        iceUfrag: '',
        icePwd: '',
        medias: [],
    };

    for (const line of offer.split('\r\n')) {
        if (line.startsWith('m=')) {
            ret.medias.push(line.slice('m='.length));
        } else if (ret.iceUfrag === '' && line.startsWith('a=ice-ufrag:')) {
            ret.iceUfrag = line.slice('a=ice-ufrag:'.length);
        } else if (ret.icePwd === '' && line.startsWith('a=ice-pwd:')) {
            ret.icePwd = line.slice('a=ice-pwd:'.length);
        }
    }

    return ret;
};

const enableStereoOpus = (section) => {
    let opusPayloadFormat = '';
    let lines = section.split('\r\n');

    for (let i = 0; i < lines.length; i++) {
        if (lines[i].startsWith('a=rtpmap:') && lines[i].toLowerCase().includes('opus/')) {
            opusPayloadFormat = lines[i].slice('a=rtpmap:'.length).split(' ')[0];
            break;
        }
    }

    if (opusPayloadFormat === '') {
        return section;
    }

    for (let i = 0; i < lines.length; i++) {
        if (lines[i].startsWith('a=fmtp:' + opusPayloadFormat + ' ')) {
            if (!lines[i].includes('stereo')) {
                lines[i] += ';stereo=1';
            }
            if (!lines[i].includes('sprop-stereo')) {
                lines[i] += ';sprop-stereo=1';
            }
        }
    }

    return lines.join('\r\n');
};

const editOffer = (offer) => {
    const sections = offer.sdp.split('m=');

    for (let i = 0; i < sections.length; i++) {
        const section = sections[i];
        if (section.startsWith('audio')) {
            sections[i] = enableStereoOpus(section);
        }
    }

    offer.sdp = sections.join('m=');
};

const generateSdpFragment = (offerData, candidates) => {
    const candidatesByMedia = {};
    for (const candidate of candidates) {
        const mid = candidate.sdpMLineIndex;
        if (candidatesByMedia[mid] === undefined) {
            candidatesByMedia[mid] = [];
        }
        candidatesByMedia[mid].push(candidate);
    }

    let frag = 'a=ice-ufrag:' + offerData.iceUfrag + '\r\n'
        + 'a=ice-pwd:' + offerData.icePwd + '\r\n';

    let mid = 0;

    for (const media of offerData.medias) {
        if (candidatesByMedia[mid] !== undefined) {
            frag += 'm=' + media + '\r\n'
                + 'a=mid:' + mid + '\r\n';

            for (const candidate of candidatesByMedia[mid]) {
                frag += 'a=' + candidate.candidate + '\r\n';
            }
        }
        mid++;
    }

    return frag;
}

class WHEPClient {
    constructor(video) {
        this.video = video;
        this.pc = null;
        this.restartTimeout = null;
        this.sessionUrl = '';
        this.queuedCandidates = [];
        this.start();
    }

    start() {
        console.log("requesting ICE servers");

        fetch(new URL('whep', window.location.href) + window.location.search, {
            method: 'OPTIONS',
        })
            .then((res) => this.onIceServers(res))
            .catch((err) => {
                console.log('error: ' + err);
                this.scheduleRestart();
            });
    }

    onIceServers(res) {
        this.pc = new RTCPeerConnection({
            iceServers: linkToIceServers(res.headers.get('Link')),
        });

        const direction = "sendrecv";
        this.pc.addTransceiver("video", { direction });
        this.pc.addTransceiver("audio", { direction });

        this.pc.onicecandidate = (evt) => this.onLocalCandidate(evt);
        this.pc.oniceconnectionstatechange = () => this.onConnectionState();

        this.pc.ontrack = (evt) => {
            console.log("new track:", evt.track.kind);
            this.video.srcObject = evt.streams[0];
        };

        this.pc.createOffer()
            .then((offer) => this.onLocalOffer(offer));
    }

    onLocalOffer(offer) {
        editOffer(offer);

        this.offerData = parseOffer(offer.sdp);
        this.pc.setLocalDescription(offer);

        console.log("sending offer");

        fetch(new URL('whep', window.location.href) + window.location.search, {
            method: 'POST',
            headers: {
                'Content-Type': 'application/sdp',
            },
            body: offer.sdp,
        })
            .then((res) => {
                if (res.status !== 201) {
                    throw new Error('bad status code');
                }
                this.sessionUrl = new URL(res.headers.get('location'), window.location.href).toString();
                return res.text();
            })
            .then((sdp) => this.onRemoteAnswer(new RTCSessionDescription({
                type: 'answer',
                sdp,
            })))
            .catch((err) => {
                console.log('error: ' + err);
                this.scheduleRestart();
            });
    }

    onConnectionState() {
        if (this.restartTimeout !== null) {
            return;
        }

        console.log("peer connection state:", this.pc.iceConnectionState);

        switch (this.pc.iceConnectionState) {
        case "disconnected":
            this.scheduleRestart();
        }
    }

    onRemoteAnswer(answer) {
        if (this.restartTimeout !== null) {
            return;
        }

        this.pc.setRemoteDescription(answer);

        if (this.queuedCandidates.length !== 0) {
            this.sendLocalCandidates(this.queuedCandidates);
            this.queuedCandidates = [];
        }
    }

    onLocalCandidate(evt) {
        if (this.restartTimeout !== null) {
            return;
        }

        if (evt.candidate !== null) {
            if (this.sessionUrl === '') {
                this.queuedCandidates.push(evt.candidate);
            } else {
                this.sendLocalCandidates([evt.candidate])
            }
        }
    }

    sendLocalCandidates(candidates) {
        fetch(this.sessionUrl + window.location.search, {
            method: 'PATCH',
            headers: {
                'Content-Type': 'application/trickle-ice-sdpfrag',
                'If-Match': '*',
            },
            body: generateSdpFragment(this.offerData, candidates),
        })
            .then((res) => {
                if (res.status !== 204) {
                    throw new Error('bad status code');
                }
            })
            .catch((err) => {
                console.log('error: ' + err);
                this.scheduleRestart();
            });
    }

    scheduleRestart() {
        if (this.restartTimeout !== null) {
            return;
        }

        if (this.pc !== null) {
            this.pc.close();
            this.pc = null;
        }

        this.restartTimeout = window.setTimeout(() => {
            this.restartTimeout = null;
            this.start();
        }, restartPause);

        if (this.sessionUrl) {
            fetch(this.sessionUrl, {
                method: 'DELETE',
            })
                .then((res) => {
                    if (res.status !== 200) {
                        throw new Error('bad status code');
                    }
                })
                .catch((err) => {
                    console.log('delete session error: ' + err);
                });
        }
        this.sessionUrl = '';

        this.queuedCandidates = [];
    }
}

/**
 * Parses the query string from a URL into an object representing the query parameters.
 * If no URL is provided, it uses the query string from the current page's URL.
 *
 * @param {string} [url=window.location.search] - The URL to parse the query string from.
 * @returns {Object} An object representing the query parameters with keys as parameter names and values as parameter values.
 */
 const parseQueryString = (url) => {
    const queryString = (url || window.location.search).split("?")[1];
    if (!queryString) return {};

    const paramsArray = queryString.split("&");
    const result = {};

    for (let i = 0; i < paramsArray.length; i++) {
        const param = paramsArray[i].split("=");
        const key = decodeURIComponent(param[0]);
        const value = decodeURIComponent(param[1] || "");

        if (key) {
            if (result[key]) {
                if (Array.isArray(result[key])) {
                    result[key].push(value);
                } else {
                    result[key] = [result[key], value];
                }
            } else {
                result[key] = value;
            }
        }
    }

    return result;
};

/**
 * Parses a string with boolean-like values and returns a boolean.
 * @param {string} str The string to parse
 * @param {boolean} defaultVal The default value
 * @returns {boolean}
 */
const parseBoolString = (str, defaultVal) => {
    const trueValues = ["1", "yes", "true"];
    const falseValues = ["0", "no", "false"];
    str = (str || "").toString();

    if (trueValues.includes(str.toLowerCase())) {
        return true;
    } else if (falseValues.includes(str.toLowerCase())) {
        return false;
    } else {
        return defaultVal;
    }
};

/**
 * Sets video attributes based on query string parameters or default values.
 *
 * @param {HTMLVideoElement} video - The video element on which to set the attributes.
 */
const setVideoAttributes = (video) => {
    let qs = parseQueryString();

    video.controls = parseBoolString(qs["controls"], true);
    video.muted = parseBoolString(qs["muted"], true);
    video.autoplay = parseBoolString(qs["autoplay"], true);
    video.playsInline = parseBoolString(qs["playsinline"], true);
};

/**
 *
 * @param {(video: HTMLVideoElement) => void} callback
 * @param {HTMLElement} container
 * @returns
 */
const initVideoElement = (callback, container) => {
    return () => {
        const video = document.createElement("video");
        video.id = "video";

        setVideoAttributes(video);
        container.append(video);
        callback(video);
    };
};

window.addEventListener('DOMContentLoaded', initVideoElement((video) => new WHEPClient(video), document.body));

</script>

</body>
</html>
